Process for dressing coal, lignite, and like materials



T. FRANZ 'July 1, -1930.

PROCESS FOR DESSING COAL, LIGNITE, AND LIKE MATERIALS VFiled Sept. 5, 1925 Patented-July'. 1,1930 7 .Y

AUNITED Asrzifrias PATENT oF-FICE. i

rnnononrmmz', or Boonen, GERMANY :PROCESS FOR DRESSING COAL, LIGNITEAND LIKE MATRIALS Application iiled September 5, 1925, Serial No; 54,843, and in Germany October 1, 1924.

I-Ieretofore, as far as mechanical treatment has been employed the dressing of coal, lignite and like materials has been eHected subyh stantially according to the same general flow sheet, viz., the same method of treatment, and diers only in respect to the machinery and apparatus used. Thelargecoal is separated in a dry state in the screening department, hand picked and loaded. The wash-coal arrives at the raw-coal bin,` whence conveyors lift it to the (usually high-level jig washer, where it is mixed with water an subjected to concentration. The concentrate consists of pure coal, which is transported directly to they place where itl is to be utilized, whilst the sludge accompanying the eiiuent from the Jig-washer is generall returned to the sepalrated fine grains thus ouling them once more, or is run intosettling tanks, allowed to settle land used as boiler'fuel. In theseknown processes the whole dressing is greatly impaired by'. the water in circulation being fouled by sudlgl and especially by salts, clay, loam and t e e.- i

In recent years, an improved method has*4 been in use, namely, removal-.of the duct by suction or screening this method having for its principal object, by adding its products to the washed coking-coal to reduce the percentage. of Water in such coking-coal, or else to procure a product which can be used by kitself as `foun powder, as coal dust or the like. On the ot er hand, a reduction of the quantity of sludge in the-j igwasher is obtained.'

HoweYer, this aim is realized in part only, `owing to the ineiiiciency of the means Jem. ployed for the purpose. The result in vievgr 1s not achieved 1f the vpercentage of moisturel of the coal exceeds a certain value. 40

ing the sludge proper have been proposed and partly used for the purpose, such as tables, vanners and the like. However, up to the present, such meanshave vonly enabled the sludge to be recovered after it has already fouled 'the cleaned coal, and only the rcoarser grains of the sludge even then. p Means and methods for the dressing of the finest slud eV `have recently become known,

among wh1chthe flotation processhas at- Certain methods and ,apparatus forfdressn tained the ygreatest importance. Only by i means of this latter is it possible totreat all the sludge of a wet-preparation plant in an economical manner and obtain practically'- complete separation into purified' lproduct 55 and waste. .Even this method, however, does I not obviate'the disadvantage that the sludge is not collected and fed to the flotation plant until it has already passed through the wet classifying apparatus (jigs, tables and the 60 the manner villustrated in the accompanying drawing, since the first step in the preparation now comprises the separation of the ma,- terial under treatment into sludge in 'suspension, on the one hand, and coarser material free from sludge, on the other hand. These portions are then treated separately by suitable processes in order to obtain the linished products desired.

' This deiiniteiinitial separation introduces -such advantages that the whole working of the wet classication process is .improved greatly, andtheresults obtained are brought vvery near to the theoretical limit ofl perfection.

at the screens,- the coals to be washed (80- 0 diameter) are passed on to the(wash ery. By means of a charging device they'are Vfed to an apparatus for separating the dry, dust fromfthe coarser coal.. Then the rough coal passes on to suitable apparatus (drums or the like) for removing such material as isv soluble or suspens'ible in the water. The separating of the washed coal from the liqu1d100 After'separating out-the-large coal (usualy 90 ly pieces ofmore than 80 mm.. in diameter) -and the sludge contained therein is effected l by means of suitable screens, a iiushing device' being used, if necessary, and -the wet sludge is drawn olf and subjected toy flotation, or treatment on tables, vanners or the like, or by suitable combinations of operations whilst the coal remaining on the screens ter used will remain nearly free. from sludge,

thus, on the one hand, improving the quality of the products, and on the otherI hand, influencingfavorably the quantitative results of the se aration process.

The otation treatment separates the sludge into clean coal and dross, v.with-perhaps some intermediate products. The dross passing away as. tailings contains nearly all the suspended clayey matter, together with fine iron-pyrites, line sand and dissolved salts, and is drawn olf separatel. and passed to the dump.' However, it may a so be subjected to clarification, and the salts contained may be removed, so as to recover a serviceable, claried water to be re-used for washing the sludge out of the coal. By this cycle of operations, I obtain the` complete separation of the sludge system from the classifying system of the cleaned coal, vso that even when the clarified water is used over again, nor argillaceous matter or the like which has 4once been washed olf can return to thewet-treatment system of cleaned coal. Of course several other combinations are possible; but, in principle, the circuit of the sludge water is completely separated from the otherwaters from the very beginning and is subjected to separate treatment. The cleaned coal recovered therefrom can alone be reunited with the puried products of the levigatedl materials.

As -mentioned previously, the second part ofthe preparation, i. e. the further treatment of the levigatedgrains,v is effect-ed in a known manner and by known means, which, according to my invention also have their own separate water circuits. The waters used in, and formed during, the preparation processes are subjected to the usual clarification, for example in spitzkasten. Here, however, the great diEerence exists, in comparison with the prior state of the art, that these waters are not contaminated by any substantial `quantity of dross or argillaceous ingredients but only byline coal resulting from the attrition of the coal itself, which will easily settle in the bottom of the spitzkasten. Experience has shown that this fine coal is of the same quality as the coal treated in the jigs, hence the iinecoal may be mixed without requiring any further treatment, with the coal treated in the jigs without impairing the latter; it may, however, also be recovered and treated separately. This ne coal, having been formed independently, does not become mixed with the sludge and, therefore, the treatment of the sludge is facilitated in comparison with prior methods.

A further advantage of the invention consists in that the waters can be well and easily clarified, owing to the absence of argillaceous out, however, influencing substantially the main liow. Thus, it will be advisable, when adding water for' washing off the sludge, not, to use any fresh Water, ut to make use of such a partial stream from the system of the Alevigated grains as, in point of composition,

is the least suitable for the washing of the levigated coal, and to add the fresh water to the latter system only. On thel other hand, it v may often be unobj ectionable to use the drainings from the purified product of the sludge system in the levigated-coal system. By such means, subordinate in themselves, the success of the invention las a Whole may be increased considerably.V

Generally, it will kbe suiiicient to adhere to the flow-sheet given above, viz., washing the sludge out of the materials to be subjected to wet classification; it will be possible, however, to use all kindsl of suitable combinations, to meet the needs of special cases, where it is desirable to remove the sludge'earlier or, vice versa, the removal of other ingredients is to be effected prior to the removal of the sludge. The first-mentioned case will arise, if the sludge be 'washed out of the rough coal prior to picking out the large coal. Vice versa, there may happen tobe a certain advantage in washing the large coal (-10 mm.) by the old methods, as this coal4 can be sold at the same price notwithstanding the higher ash content, and there is, therefore, no reason for improving this coal by washing. At4 the time, however, there is a growing tendency to lower the ash content in coking-coal, i. e. small coal below 10 mm., in order to Vobtain amore valuable coke therefrom. In such a case, according to the invention, the process is so conducted that washing out the sludge begins only when said small coal is being treated, and from this point onwards the classification is carried out on two definitely separated products; sludge and levigated material. Accordpoint and to direct them to other places withing to the principle of the invention-it will be rate circuit or to` feed it lto the-system for i washing out the sludge. j

If the main product of thewet preparatlon be small coal, then it will seem appropriate first to disintegrate the large coal and not to wash out the sludge till alfter said coal has been crushed. v

If intermediate products be formed in the plant and crushed for further preparation,

postponed conveniently until 'after said crushing. The levigation( of these intermedlate products may take place in a separate circuit or they maybe treated jointly with other l 'coals to be freed from sludge.

It may be advantageous, e.` g. when a very pure .product is. required to accomplish the 'processof removing the slud not in one operation only but to carry .1t through in stages, whereby also intermediate disintegration or otherintermediat'e voperations may be performed between the separate stages.

- -As hasbeen mentioned repeatedly in the4 coarser grains; the coarser grains are then.

passed to the washery in which the mass is subjected to a `Washing operation; the mass and the washing'water arethen discharged from thewashery and pass over screens which separate thesolid coal from the liquid sludge. The lsolid coal-'is passed to the w,et classifier in which the coal particles ranging in size from' 10 to 80 mm. are separated from 'those ranging `from 1Q mm. to 0, each class being passed'on'to suitable jigs and washed. The liquid or'wet sludge is .subjected to ilotation, which separates the sludge into clean coal and dross. covered and the dross passed tothe dump.

' The water used in the above operations is subjected vto a clarifying process in a spitzkasten, and thereafter used again. in Ythe sludge circuit, fresh water beingaddedtothe general system via the coal washing circuit.

lean coal is recovered from the spltzkasten and mixed with the :fine coal treated in the gis-clam: ...1. A method for the preparation vof coal, lignite 'and similar substances containing soluble and suspensible'materialsfaccordinv te which the mass. tzbet'rea'ted is subjecte i to jafwashing' operationin yorder' to remove then the washing out of the sludge will be- The clean coal is re-f.

and c oarsermaterial being kept apart and treated separately during the succeeding ;the sludge, the resulting products, sludge stages ofthe preparation, and the .'eiiluent v Waters from the treatment of the sludge are re-utilized in a separate circuit for the treatment of the sludge. l

2.v A method for the preparationof coal, lignite and similar substances containing soluble and suspensible materials according to which the mass to be treated is subjected to a Washing `operation in order to remove the sludge, the resulting roducts, sludge and coarser material being ept apart and treat- -ed separately during the succeeding stages of -the preparation, and the eilluent watersfrom thetreatment of the sludge are re-utilized in a separate circuit for the treatmentrv of the sludge, an intermediate clarifying operation .of said waters being effected prior to rtheir re-utilization.

i, 3. A method lignite and similar substances containing se' l for the'preparation of coal,

soluble and suspensible materials according to which'the mass to be treated is subjected to ar washing operation in order to remove the sludge, the resultin products, sludge and 'coarser material being ept yapart and treated separately duringthe succeeding stages of the preparation, and the eiiuent waters from the treatment of the coarser material are diverted into a separate circuit in order to be 12e-utilized in connection with the treatment of the'coarser material in whole or in part.

4..A method for .the

stances containing ble and suspensible materials according to which the mass to be treated Vis subjected to awashin operation in order to 'remove the sludge, t e resulting products, sludge and coarser material bein kept apart and -treated separately during t e succeeding stages of the preparation, and the eiiiuent waters from the treatment of the coarser material are diverted into a separate circuit 'in order to be re-utilized inconnection with the treatmentN an intermediate clarifying operation o f saidwaters being efected prior `to their lre-utilizal ltion.

ftofa washing operation inorder to remove the sludge,'the resulting products,.sludge and fof the coarser material in whole or in part, y

coarser material being kept apart and treated' 1` l .separately-during the 'succeeding stages of the preparation, and the liuids appearing Y `atjsolne points of the separate circuits [areA Withdrawn from their respective circuits and conducted'to vother circuits of similar uids'.

v preparation of. coal, lignite'z and similar,rv su stances `containing soluble and suspe'nsible` materials accordingA lasl to which the mass to be treated is subjected to a Washing operation in order to remove the sludge, the resulting products, sludge and coarser material being kept apart and treated 5 separately during the succeeding stages of the preparation, and the iuids appearmg atA some points ofthe separate circuits are Withf drawn from their respective circuits and conducted to other circuits of similar fluids, and intermediate clarifying operations of said fluids being effected at desired points. In Witness whereof I have signed this specifcation.

THEODOR FRANZ. 

